class_docstr: Main coreference resolution algorithm
docstr: Clean up and prepare one cluster for each mention
docstr_tok: ["Clean","up","and","prepare","one","cluster","for","each","mention"]
code: def _prepare_clusters(self):
      """
      Clean up and prepare one cluster for each mention
      """
      self.mention_to_cluster = list(range(len(self.data.mentions)))
      self.clusters = dict((i, [i]) for i in self.mention_to_cluster)
      self.mentions_single_scores = {}
      self.mentions_pairs_scores = {}
      for mention in self.mention_to_cluster:
          self.mentions_single_scores[mention] = None
          self.mentions_pairs_scores[mention] = {}
  
imports: import os
  import spacy
  import numpy
  from neuralcoref.train.utils import PACKAGE_DIRECTORY, SIZE_SINGLE_IN
  from neuralcoref.train.compat import unicode_
  from neuralcoref.train.document import Document, MENTION_TYPE, NO_COREF_LIST
label_desc: Use image node_id 2 for calling the Coref obj's underlying member method code with example usage: obj._prepare_clusters() without return types